Two-dimensional (2D) and three-dimensional (3D) digital image technology has recently been tapped as a tool to assist in dental and orthodontic treatment. Many treatment providers use some form of digital image technology to study the dentitions of patients. U.S. patent application Ser. No. 09/169,276 describes the use of 2D and 3D image data in forming a digital model of a patient's dentition, including models of individual dentition components. That application also describes using the digital dentition models in developing an orthodontic treatment plan for the patient, as well as in creating one or more orthodontic appliances to implement the treatment plan.
Some of these orthodontic appliances are rigid, shell-like devices that fit over the patient's teeth, applying the forces necessary to move the teeth to prescribed final positions. Such an appliance can be produced by pressure forming a sheet of material around a positive mold. In general, the positive mold is a solid block manufactured from a resin-based material in a rapid prototyping process.